Have you ever neglected to sufficiently tighten the gas cap after refueling your car? If you have a car built after 1996, it's likely to have triggered the "Check Engine" dashboard idiot light, even though nothing is wrong with your car.
The only way to reset the light is through the car's On-board diagnostics (OBD) system (or you might be able to do it by disconnecting the battery terminals). Most car repair shops will charge to reset the light.
Just for the heck of it, I bought a Bluetooth OBD code reader for $(removed) on Amazon to see what kind of information I could could obtain. It's a blue plastic thumb-sized gadget that plugs into your car's OBDII port (look for a white socket on under the dashboard on the driver's side). It is meant for Android phones. If you have an iPhone, try a WiFi version for $(removed)
I had no trouble pairing my Android phone to it, and I used a free app called Torque Lite to translate the data into English. It allows you to check the real reason the Check Engine light went on, and also lets you reset it if you wish. The next time my check engine light turns on, I'm going to use it to find out what the deal is before taking my car to a repair shop.
You can keep the scanner plugged into your port, and as long as you are running the app on your phone, it'll log the data, which you can email as a comma-delimited file.
The data scanner comes with a little CD-ROM, but you don't need it. Throw it away, because some reviewers on Amazon say it has a trojan on it.
